Electroreduction of chloroacetic acids (mono-, di- and tri-) at polyNi(II)-tetrasulfonated phthalocyanine gold modified electrode

The electroformation of polyNi(II)-tetrasulfonated phthalocyanine (poly-NiTSPC) film, on gold electrodes from an alkaline solution was investigated in order to improve the electrochemical detection of haloacetic acids (mono-, di- and tri-chloroacetic). The data obtained were compared to those obtained at bare Au electrode. The electrocatalytic activity of the poly-NiTSPC towards the chloroacetic acids reduction, promotes a negative shift of the peak potential (by ca. 250 mV) and an increase of the current intensity (by ca. 25%) compared to bare Au electrode. The concentration of chloride-ion in solution was obtained during electrolysis for each chloroacetic acid; and the number of electrons involved in haloacetic acids reduction and heterogeneous rate constant (k) were evaluated by rotating disk electrode (RDE). These studies showed that the mechanism of catalytic reduction of chloroacetic acids can be expressed on the basis that the current-determining step in the electroreduction of chloroacetate ions must involve the removal of a halogen atom from the anion. The modified electrode showed an excellent sensitivity and detection limit towards haloacetic acid reduction.